2. During the rainy season the water level in a certain lake rises. A road already exists through the school that goes over a circular lake. The local government wants to build another road through the school that connects to this road but not go through the lake. The city engineer can measure the road that already exists, and he finds that the bridge portion of the road is 5 kilometers, and the portion of the road from the bridge to where the new road will be is 4 km. How long the road will be constructed. (Hint: Use tangent line).